Dynamics of cereal leafhoppers number (Homoptera, Auhenorrhyncha) depending on sowing time and winter wheat seeding rate during the whole vegetation in the conditions of the forest-steppe of Ukraine

Abstract

For the period 2014-2017 in the Forest-Steppe of Ukraine, the most numerous and permanent grass leafhopper species in winter wheat crops were striped (48 %) and six-point (31%). The seasonal dynamics of the pests number during the growing season was studied. The maximum number of phytophages on crops was recorded at the maturation stage (150,5-200,0 indiv./100 sweeps with thenet at100% colonization) and at tillering stage (120,5-150,2indiv./m² at plant colonization 60,2-75,1%) by late sowing. The high leafhoppers density was observed at a seeding rate of 5.5 mln./ha at maturation stage and tillering of the crop (180,0 indiv./100 sweeps with the net and 150,0 indiv./m²). The late term of sowing and wheat seeding rate increase leads to leafhopper number increase more than twice at milky and wax ripeness stage and tillering. To determine the leafhoppers economic threshold of harmfulness (EHT) , harmful phytophagous insects were monitored in winter wheat crops in two crop vegetation periods: spring-summer and autumn. The economic threshold of harmfulness of cereal leafhoppers during autumn winter wheat vegetation is 70,0-150,0 indiv./m², at the heading stage - milky ripeness - 100 adults/50 sweeps with the net or 200-300 larvae/m².